VB对ComboBox输入框的输入进行检查，下拉ComboBox中的值，输入错误会有提示。临时标签，用来获得焦点，使组合框能够失去焦点，并在失去焦点时进行有效性检查，若输入的数据不在列表中，请重新输入。-VB input ComboBox input box is checked, the value in the drop-down ComboBox, input error will be prompted. Temporary tag to get the focus, so the combo box to lose focus, and validity check when they lose focus, if the input data is not in the list, please re-enter.